The present invention relates to laminating resins. More particularly, the present invention relates to laminating resins having a low volatile monomer content.
Laminating resins have long been used in conjunction with solid materials, typically those which are thermoset or thermoplastic materials which are reinforced by fibers. Typically, the resins are coated, sprayed, or brushed onto components which are used as panels forming the exterior bodies of vehicles, marine vessels, and other molded articles. Subsequently, the component is subjected to specified conditions such as temperature so as to cure the resin. The laminated resin is useful in that it imparts desirable physical properties to the panel. In particular, the cured resin typically displays adequate strength, toughness, elongation, heat distortion temperature, and chemical resistance properties. Moreover, the resin is desirable in that it provides a finished appearance to the exterior body.
A traditional laminating resin is typically formed from several components including unsaturated polyesters and bisphenol compounds such as difunctional bisphenol-A acrylic esters. The resin also typically includes a volatile monomer diluent such as styrene or vinyl toluene to facilitate employing the resin as a liquid.
The use of volatile monomers, however, have become disfavored due to alleged increased environmental risks. For example, U.S. Pat. No. 5,393,830 to Smeal et al. proposes a laminating resin which employs a reduced amount of styrene so as to meet a specified volatile emission test standard. The resin comprises a polyester resin, ethylene glycol dimethacrylate, vinyl toluene, cyclohexyl methacrylate, and bisphenol-A dimethacrylate.
The use of bisphenol-A dimethacrylate in a laminating resin, however, suffers from various drawbacks. For example, utilizing the bisphenol compound in forming a laminating resin is unduly complex from a processing standpoint in that multiple lengthy steps are needed before achieving the final resin end product. Moreover, the bisphenol-A dimethacrylate material is often one of the more expensive components used in formulating the laminating resin.
In view of the above, it is an object of the present invention to provide a laminating resin composition which utilizes a reduced level of volatile monomer diluent such as styrene.
It is a further object of the present invention to provide a laminating resin exhibiting good end properties which employs relatively less expensive starting material and is produced from a simpler process relative to conventional processes.
To these ends and others, the present invention provides a laminating resin which has low volatile monomer content and exhibits advantageous physical properties, especially with respect to toughness. Specifically, the laminating resin comprises an unsaturated polyester resin, a vinyl ester resin, a polyfunctional acrylate, and less than about 15 percent by weight of vinyl monomer.
The unsaturated polyester resin preferably has a weight average molecular weight ranging from about 300 to 2000. In such an embodiment, the laminating resin further comprises a component selected from the group consisting of acrylic acid, methacrylic acid, cinnamyl alcohol, crotonic acid, cinnamic acid, sorbic acid, maleic acid, fumaric acid, itaconic acid, benzoic acid, benzyl alcohol, cyclohexanol, 2-ethyl hexanol, trimethylol propane diallyl ether, and mixtures thereof.
The vinyl ester resin preferably has a weight average molecular weight ranging from about 450 to 1500 and is the reaction product of an unsaturated polycarboxylic acid or anhydride with an epoxy resin.
The laminating resin may optionally contain other components. In one embodiment, the laminating resin further comprises a dicyclopentadiene resin.
In a preferred embodiment, the laminating resin comprises from about 25 to 50 percent by weight of an unsaturated polyester resin, from about 1 to 75 percent by weight of a vinyl ester resin, from about 1 to 15 percent by weight of a polyfunctional acrylate, less than about 15 percent by weight of a vinyl monomer, and from about 5 to 25 percent by weight of a dicyclopentadiene resin.
The invention also relates to an article of manufacture. The article of manufacture comprises a substrate comprising reinforcing fibrous material and a laminating resin coated onto the substrate. The laminating resin comprises an unsaturated polyester resin, a vinyl ester resin, a polyfunctional acrylate, and less than about 15 percent by weight of a vinyl monomer.
As summarized above, the present invention relates to a laminating resin which includes an unsaturated polyester resin, a vinyl ester resin, a polyfunctional acrylate, and less than about 15 percent by weight of a vinyl monomer. For the purposes of the invention, the term xe2x80x9claminating resinxe2x80x9d is to be broadly interpreted to include any resin which may be applied to or coated on a suitable substrate. Laminating resins, for example, may include gel coat resins.
The unsaturated polyester resin is typically formed from the reaction between a polybasic acid or anhydride and an alcohol. Known and suitable processes for preparing such polyesters may be employed for the purpose of the present invention.
Suitable polybasic acids or anhydrides thereof include dicarboxylic acids such as, but not limited to, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexane dicarboxylic acid, succinic acid, adipic acid, sebacic acid, azealic acid, malonic acid, alkenyl succinic acids such as n-dodecenylsuccinic acid, docecylcucinic acid and octadecenylsuccinic acid, and mixtures thereof. Lower alkyl esters of any of the above may also be employed.
The polybasic acid or anhydride may be employed in any suitable amount, preferably of from about 20 to 55 percent based on the weight of the unsaturated polyester resin.
Any alcohols which are appropriate in polyester-forming reactions are utilized. Such compounds include, but are not limited to, ethylene glycol, diethylene propylene glycol, diethylene glycol, neopentyl glycol, dipropylene glycol, poly-tetramethylene glycol, bispolyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(3.3)-2,2-bis(4-bis(4-hydroxyphenyl)propane, polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane. Diols may be employed and include, for example, 1,5-pentanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Polyhydric alcohols are also suitable and include, for example, sorbitol, 1,2,3,6-hexatetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methyl propanetriol, 2-methyl 1,2,4-butanetriol, trimethylol ethane, trimethylol propane, and 1,3,5-trihydroxyethyl benzene. Mixtures of any of the above may be used.
The alcohols may be employed in any suitable amount, preferably of from about 10 to 60 percent based on the weight of the unsaturated polyester resin.
Although not wishing to be bound by any theory, the molecular weight of the unsaturated polyester resin is believed to be controlled by end capping the polyester resin with a monovalent radical under known and suitable processing conditions. In this instance, the unsaturated polyester resin preferably has a weight average molecular weight ranging from about 300 to 2000, and more preferably from about 500 to 1000. The monovalent radical used to end cap the polyester resin may be selected from the group consisting of acrylic acid, methacrylic acid, cinnamyl alcohol, crotonic acid, cinnamic acid, sorbic acid, maleic acid, fumaric acid, itaconic acid, benzoic acid, benzyl alcohol, cyclohexanol, 2 ethylhexanol, and trimethylol propane diallyl ether. Mixtures of the above may be used. The monovalent radical is preferably employed in an amount ranging from about 20 to 60 percent based on the weight of the unsaturated polyester resin.
Known and appropriate esterification catalysts may be employed in the reaction which forms the unsaturated polyester resin. As an example, esterification catalysts may include organotin oxides and titanates such as stannous oxide, dibutyl tin oxide, dibutyl tin bis(ethylhexanoate), titanium isoproproxide, titanium ethoxide, and mixtures thereof. The catalysts may be employed in any suitable amount, preferably of from about 0.005 to 0.02 percent based on the weight of the polyester resin.
The laminating resin preferably employs from about 25 to 60 percent by weight of unsaturated polyester resin, more preferably from about 30 to 50 percent by weight, and most preferably from about 30 to 40 percent by weight.
The vinyl ester resin employed in the laminating resin is preferably of low molecular weight. The term xe2x80x9clow molecular weightxe2x80x9d refers to the vinyl ester resin preferably having a weight average molecular weight ranging from about 450 to 3000. Most preferably, the molecular weight ranges from about 500 to 1500. For the purposes of the invention, a vinyl ester resin typically includes a suitable reaction product of an unsaturated monocarboxylic acid or anhydride with an epoxy resin. The reactants are typically employed in amounts which provide a ratio of acid groups per epoxy group ranging from about 0.95:1 to about 1.05:1, with the ratio preferably being about 1:1. The reaction between the unsaturated monocarboxylic acid or anhydride and epoxy resin is typically carried out at temperatures ranging from about 90xc2x0 C. to 130xc2x0 C., preferably from about 100xc2x0 C. to 120xc2x0 C., and more preferably from about 105xc2x0 C. to 110xc2x0 C., for a sufficient time to complete the reaction. The reaction is usually considered complete when the percent acid remaining has reached a value of 1 or less. The reaction time is usually from about 3 to 6 hours.
Exemplary acids and anhydrides which may be used in forming the vinyl ester resins include (meth)acrylic acid or anhydride, xcex1-phenylacrylic acid, xcex1-chloroacrylic acid, crotonic acid, mono-methyl and mono-ethyl esters of maleic acid or fumaric acid, vinyl acetic acid, sorbic acid, cinnamic acid, and the like.
Epoxy resins which may be employed are known and include virtually any reaction product of a polyfunctional halohydrin, such as epichlorohydrin, with a phenol or polyhydric phenol. Suitable phenols or polyhydric phenols include, for example, resorcinol, tetraphenol ethane, and various bisphenols such as bisphenol-A, 4,4xe2x80x2-dihydroxydiphenylsulfone, 4,4xe2x80x2-dihydroxy, biphenyl, 4,4xe2x80x2-dihydroxydiphenylmethane, 2,2xe2x80x2-dihydroxydiphenyloxide, and the like. In accordance with the invention, the amount of bisphenol-A is limited to quantities which are suitable.
Any appropriate epoxy resin may be used in forming the vinyl ester resin. The epoxy resins typically have an average of more than one vicinal group per molecule with an unsaturated polycarboxylic acid. Specific bisphenol epoxy resins employed in forming the vinyl ester resins are represented by the formula: 
wherein X and A are defined herein; R3 is H , xe2x80x94CH3, or an alkyl from 1 to 4 carbon atoms; and p ranges from 0 to 15. Novolac epoxy resins may also be used and include those represented by the formula: 
wherein R3 is described herein; R4 is H or an alkyl group; and q ranges from 1 to 15.
Specific epoxy compounds include various glycidyl ethers of resorcinol; catechol; hydroquinone; bisphenol A; fluorine, phenol-, or cresol-aldehyde resins and halogenated (e.g., bromine) substituted derivatives thereof. Mixtures of any of the above epoxy resins may be used.
A catalyst may be used for promoting the reaction between the unsaturated monocarboxylic acid or anhydride and the epoxy resin. Suitable catalysts include, for example, tris(dimethylamynomethyl)phenol, tetraethyl ammonium bromide, tetramethyl ammonium chloride, zirconium hexanoate, triphenyl phosphine, and the like. Any combination of the above may be used. Particularly suitable catalysts include, for example zirconium hexanoate or triphenyl phosphine, or any combination thereof and the like. The catalysts are usually employed in amounts of from about 0.03 to about 0.15, preferably from about 0.05 to 0.1, most preferably from about 0.06 part of catalyst per 100 parts of resultant mixture of the polycarboxylic acid or anhydride and the epoxy resin.
The laminating resin composition may be formed from various percentages of vinyl ester resin. Preferably, the laminating resin composition comprises between about 1 to 75 percent by weight of the vinyl ester resin, more preferably from about 1 to 70 percent by weight, and most preferably from about 5 to 40 percent by weight.
Any suitable polyfunctional acrylate may be used in the laminating resin composition, including those described, for example, in U.S. Pat. No. 4,916,023 to Kawabata et al., the disclosure of which is incorporated by reference herein in its entirety. Such compounds include ethylene glycol (EG) dimethacrylate, butanediol demethacrylate, hydroxypropyl methacrylate, hydroxyethyl methacrylate, and the like. The polyfunctional acrylate which may be used in the present invention can be represented by the general formula: 
wherein at least four of the represented R""s present are (meth)acryloxy groups, with the remainder of the R""s being an organic group except (meth)acryloxy groups, and n is an integer from 1 to 5. Examples of polyfunctional acrylates include ethoxylated trimethyolpropane triacrylate, trimethyolpropane tri(meth)acrylate, trimethyolpropane triacrylate, trimethylolmethane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The preferred polyfunctional acrylate is EG dimethacrylate. Mixtures of any of the above may be used in the laminating resin.
The laminating resin composition may comprise various amounts of the polyfunctional acrylate. The laminating resin composition preferably comprises from about 1 to 15 percent by weight of the polyfunctional acrylate, and more preferably from about 3 to 10 percent by weight.
A vinyl monomer may also be included in the laminating resin composition, with the laminating resin containing less than about 15 percent by weight of the vinyl monomer. In accordance with the invention, such amounts of monomer are not believed to be hazardous. Using styrene as an example, one is referred to xe2x80x9cProduct Safety Bulletin: Styrene Monomerxe2x80x9d, The Environmental, Health, and Safety Department of the Arco Chemical Company of Newtown Square, Pa., (March 1994). As known, the potential risk of any monomer depends on processing conditions relating to temperature, pressure, catalyst concentration, and monomer concentration. For example, OSHA has suggested an allowable 8 hours time weight average styrene exposure level of 50 ppm. Such monomers may include those such as, for example, styrene and styrene derivatives such as alpha-methylstyrene, p-methyl styrene, divinyl benzene, divinyl toluene, ethyl styrene, vinyl toluene, tert-butyl styrene, monochlorostyrene, dichlorostyrene, vinyl benzyl chloride, fluorostyrene, and alkoxystyrenes (e.g., paramethoxystyrene). Other monomers which may be used include, for example, diallyl phthalate, hexyl acrylate, octyl acrylate, octyl methacrylate, diallyl itaconate, diallyl meleate, hydroxyethyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. Mixtures of the above may also be employed. The vinyl monomer more preferably comprises less than about 15 percent by weight of the laminating resin, and most preferably less than about 10 percent by weight of the laminating resin.
The laminating resin may also include other various components. For example, the resin may include dicyclopentadiene resin in any appropriate amount, preferably ranging from about 5 to 45 percent by weight of the laminating resin.
The laminating resin composition may include an agent such as an organic peroxide compound to facilitate curing of the composition. Exemplary organic peroxides may be used and include, for example, cumene hydroperoxide, methyl ethyl ketone peroxide, benzoyl peroxide, acetyl acetone peroxide, 2,5-dimethylhexane-2,5-dihydroperoxide, tert-butyl peroxybenzoate, di-tert-butyl perphthalate, dicumylperoxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane 3, bis(tert-butylperoxyisopropyl)benzene di-tert-butyl peroxide, 1,1-di(tert-amylperoxy)-cyclohexane, 1,1-di-(tert-butylperoxy)-3,3,5-trymethylcyclohexane, 1,1-di-(tert-butylperoxy)-cyclohexane, 2,2-di-(tert-butylperoxy)-butane, n-butyl 4,4-di-(tert-butylperoxy)-valerate, ethyl 3,3-di-(tert-amylperoxy)-butyrate, ethyl 3,3-di-(tert-butylperoxy)-butyrate and the like. Mixtures of any of the above may be used. The agent is preferably employed in an amount from about 1 to 2.5 percent based on the weight of the laminating resin, more preferably from about 1 to 1.5 percent by weight, and most preferably from about 1 to 1.25 percent by weight.
Suitable curing accelerators or promoters may also be used and include, for example, cobalt naphthanate, cobalt otoate, N,N-dimethyl aniline, N,N-dimethyl acetamide, and N,N-dimethyl para-toluidine. Mixtures of the above may be used. The curing accelerators or promoters are preferably employed in amounts from about 0.05 to 1.0 percent by weight, more preferably from about 0.1 to 0.5 percent by weight, and most preferably from about 0.1 to 0.3 percent by weight of the laminating resin.
Additional additives known by the skilled artisan may be employed in the laminating resin composition of the present invention including, for example, paraffins, fatty acids, fatty acid derivatives, lubricants, and shrink-reducing additives. Various percentages of these additives can be used in the laminating resin composition.
The present invention also relates to an article of manufacture. The article of manufacture may be any product which employs a laminating resin, and typically includes marine vessels, vehicles, and aircraft. More specifically, the article includes a substrate with the laminating resin composition coated thereon. The substrate may be made of any appropriate material and typically includes fibrous reinforced material such as those formed of thermoset or thermoplastic resins. The fibers which may be used typically include, but are not limited to, fibrous glass, carbon fibers, aromatic polyamide fibers, inorganic fibers, and the like.
The laminating resin composition may be prepared in accordance with any of the suitable processes known in the art and described further herein. The laminating resin composition may be applied by a suitable method such as coating (e.g., spraying or brushing) to the substrate so as to form a coat. Preferably, the thickness of the laminating resin coat ranges from about 0.2 to 3.0 mm. Coating operations are usually performed at temperatures ranging from about 10xc2x0 C. to 35xc2x0 C. The applied laminating resin and substrate is typically then cured using appropriate means at temperatures ranging from about 10xc2x0 C. to 35xc2x0 C. for about 1 to 120 minutes.
The following examples are provided to illustrate the present invention, and should not be construed as limiting thereof.